/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.aop.aspectj.annotation;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.AfterReturning;
import org.aspectj.lang.annotation.AfterThrowing;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.AjType;
import org.aspectj.lang.reflect.AjTypeSystem;
import org.aspectj.lang.reflect.PerClauseKind;
import org.springframework.aop.framework.AopConfigException;
import org.springframework.core.ParameterNameDiscoverer;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.lang.Nullable;

import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;

/**
 * Abstract base class for factories that can create Spring AOP Advisors
 * given AspectJ classes from classes honoring the AspectJ 5 annotation syntax.
 *
 * <p>This class handles annotation parsing and validation functionality.
 * It does not actually generate Spring AOP Advisors, which is deferred to subclasses.
 *
 * @author Rod Johnson
 * @author Adrian Colyer
 * @author Juergen Hoeller
 * @since 2.0
 */
public abstract class AbstractAspectJAdvisorFactory implements AspectJAdvisorFactory {

    private static final String AJC_MAGIC = "ajc$";

    private static final Class<?>[] ASPECTJ_ANNOTATION_CLASSES = new Class<?>[]{
            Pointcut.class, Around.class, Before.class, After.class, AfterReturning.class, AfterThrowing.class};


    /**
     * Logger available to subclasses.
     */
    protected final Log logger = LogFactory.getLog(getClass());

    protected final ParameterNameDiscoverer parameterNameDiscoverer = new AspectJAnnotationParameterNameDiscoverer();

    /**
     * Find and return the first AspectJ annotation on the given method
     * (there <i>should</i> only be one anyway...).
     */
    @SuppressWarnings("unchecked")
    @Nullable
    protected static AspectJAnnotation<?> findAspectJAnnotationOnMethod(Method method) {
        for (Class<?> clazz : ASPECTJ_ANNOTATION_CLASSES) {
            AspectJAnnotation<?> foundAnnotation = findAnnotation(method, (Class<Annotation>) clazz);
            if (foundAnnotation != null) {
                return foundAnnotation;
            }
        }
        return null;
    }

    @Nullable
    private static <A extends Annotation> AspectJAnnotation<A> findAnnotation(Method method, Class<A> toLookFor) {
        A result = AnnotationUtils.findAnnotation(method, toLookFor);
        if (result != null) {
            return new AspectJAnnotation<>(result);
        } else {
            return null;
        }
    }

    /**
     * We consider something to be an AspectJ aspect suitable for use by the Spring AOP system
     * if it has the @Aspect annotation, and was not compiled by ajc. The reason for this latter test
     * is that aspects written in the code-style (AspectJ language) also have the annotation present
     * when compiled by ajc with the -1.5 flag, yet they cannot be consumed by Spring AOP.
     */
    @Override
    public boolean isAspect(Class<?> clazz) {
        return (hasAspectAnnotation(clazz) && !compiledByAjc(clazz));
    }

    private boolean hasAspectAnnotation(Class<?> clazz) {
        return (AnnotationUtils.findAnnotation(clazz, Aspect.class) != null);
    }

    /**
     * We need to detect this as "code-style" AspectJ aspects should not be
     * interpreted by Spring AOP.
     */
    private boolean compiledByAjc(Class<?> clazz) {
        // The AJTypeSystem goes to great lengths to provide a uniform appearance between code-style and
        // annotation-style aspects. Therefore there is no 'clean' way to tell them apart. Here we rely on
        // an implementation detail of the AspectJ compiler.
        for (Field field : clazz.getDeclaredFields()) {
            if (field.getName().startsWith(AJC_MAGIC)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public void validate(Class<?> aspectClass) throws AopConfigException {
        // If the parent has the annotation and isn't abstract it's an error
        if (aspectClass.getSuperclass().getAnnotation(Aspect.class) != null &&
                !Modifier.isAbstract(aspectClass.getSuperclass().getModifiers())) {
            throw new AopConfigException("[" + aspectClass.getName() + "] cannot extend concrete aspect [" +
                    aspectClass.getSuperclass().getName() + "]");
        }

        AjType<?> ajType = AjTypeSystem.getAjType(aspectClass);
        if (!ajType.isAspect()) {
            throw new NotAnAtAspectException(aspectClass);
        }
        if (ajType.getPerClause().getKind() == PerClauseKind.PERCFLOW) {
            throw new AopConfigException(aspectClass.getName() + " uses percflow instantiation model: " +
                    "This is not supported in Spring AOP.");
        }
        if (ajType.getPerClause().getKind() == PerClauseKind.PERCFLOWBELOW) {
            throw new AopConfigException(aspectClass.getName() + " uses percflowbelow instantiation model: " +
                    "This is not supported in Spring AOP.");
        }
    }


    /**
     * Enum for AspectJ annotation types.
     *
     * @see AspectJAnnotation#getAnnotationType()
     */
    protected enum AspectJAnnotationType {

        AtPointcut, AtAround, AtBefore, AtAfter, AtAfterReturning, AtAfterThrowing
    }


    /**
     * Class modelling an AspectJ annotation, exposing its type enumeration and
     * pointcut String.
     *
     * @param <A> the annotation type
     */
    protected static class AspectJAnnotation<A extends Annotation> {

        private static final String[] EXPRESSION_ATTRIBUTES = new String[]{"pointcut", "value"};

        private static Map<Class<?>, AspectJAnnotationType> annotationTypeMap = new HashMap<>(8);

        static {
            annotationTypeMap.put(Pointcut.class, AspectJAnnotationType.AtPointcut);
            annotationTypeMap.put(Around.class, AspectJAnnotationType.AtAround);
            annotationTypeMap.put(Before.class, AspectJAnnotationType.AtBefore);
            annotationTypeMap.put(After.class, AspectJAnnotationType.AtAfter);
            annotationTypeMap.put(AfterReturning.class, AspectJAnnotationType.AtAfterReturning);
            annotationTypeMap.put(AfterThrowing.class, AspectJAnnotationType.AtAfterThrowing);
        }

        private final A annotation;

        private final AspectJAnnotationType annotationType;

        private final String pointcutExpression;

        private final String argumentNames;

        public AspectJAnnotation(A annotation) {
            this.annotation = annotation;
            this.annotationType = determineAnnotationType(annotation);
            try {
                this.pointcutExpression = resolveExpression(annotation);
                Object argNames = AnnotationUtils.getValue(annotation, "argNames");
                this.argumentNames = (argNames instanceof String ? (String) argNames : "");
            } catch (Exception ex) {
                throw new IllegalArgumentException(annotation + " is not a valid AspectJ annotation", ex);
            }
        }

        private AspectJAnnotationType determineAnnotationType(A annotation) {
            AspectJAnnotationType type = annotationTypeMap.get(annotation.annotationType());
            if (type != null) {
                return type;
            }
            throw new IllegalStateException("Unknown annotation type: " + annotation);
        }

        private String resolveExpression(A annotation) {
            for (String attributeName : EXPRESSION_ATTRIBUTES) {
                Object val = AnnotationUtils.getValue(annotation, attributeName);
                if (val instanceof String) {
                    String str = (String) val;
                    if (!str.isEmpty()) {
                        return str;
                    }
                }
            }
            throw new IllegalStateException("Failed to resolve expression: " + annotation);
        }

        public AspectJAnnotationType getAnnotationType() {
            return this.annotationType;
        }

        public A getAnnotation() {
            return this.annotation;
        }

        public String getPointcutExpression() {
            return this.pointcutExpression;
        }

        public String getArgumentNames() {
            return this.argumentNames;
        }

        @Override
        public String toString() {
            return this.annotation.toString();
        }
    }


    /**
     * ParameterNameDiscoverer implementation that analyzes the arg names
     * specified at the AspectJ annotation level.
     */
    private static class AspectJAnnotationParameterNameDiscoverer implements ParameterNameDiscoverer {

        @Override
        @Nullable
        public String[] getParameterNames(Method method) {
            if (method.getParameterCount() == 0) {
                return new String[0];
            }
            AspectJAnnotation<?> annotation = findAspectJAnnotationOnMethod(method);
            if (annotation == null) {
                return null;
            }
            StringTokenizer nameTokens = new StringTokenizer(annotation.getArgumentNames(), ",");
            if (nameTokens.countTokens() > 0) {
                String[] names = new String[nameTokens.countTokens()];
                for (int i = 0; i < names.length; i++) {
                    names[i] = nameTokens.nextToken();
                }
                return names;
            } else {
                return null;
            }
        }

        @Override
        @Nullable
        public String[] getParameterNames(Constructor<?> ctor) {
            throw new UnsupportedOperationException("Spring AOP cannot handle constructor advice");
        }
    }

}
